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GR Research (incomplete) speaker measurement methodology.

Deanxxx

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In answer to the following question: "It would be great if [GR Research] could include directivity index, estimated in-room response, distortion, and polar plots [in measurements]" Danny replied, "Directivity can be seen in the off axis responses. What the response might look like in a room can also be derived from that data. Distortion measurements taken outside of an anechoic chamber are irrelevant."

hmmm
 

ThatSoundsGood

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At least he posts some measurements. Many speaker designers/makers don't post any. Sure, it would be great if he used a Klippel but at least his method is more transparent than a lot of others.
 
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Deanxxx

Deanxxx

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At least he posts some measurements. Many speaker designers/makers don't post any. Sure, it would be great if he used a Klippel but at least his method is more transparent than a lot of others.
Sure, fair point. Most of the important stuff is presented but my point (and the title of this post) is about how incomplete his method is. To the degree of being only partially useful IMHO.
 

Curvature

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You already have this review: https://www.audiosciencereview.com/...research-lgk-2-0-speaker-review-a-joke.34783/

Other views of the same data: https://www.audiosciencereview.com/...-2-0-speaker-review-a-joke.34783/post-1212640 https://www.audiosciencereview.com/...2-0-speaker-review-a-joke.34783/#post-1212484

Compare the GR research measurements below. They are gated, smoothed, have no LF information and show little MF/HF detail. https://gr-research.com/product/lgk-2-0/

off-axis-response.jpg

index.php

index.php


Without distortion data you would think this little speaker is ok.
 

fineMen

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At least he posts some measurements. Many speaker designers/makers don't post any. Sure, it would be great if he used a Klippel but at least his method is more transparent than a lot of others.
For me that doesn't sound like a good argument. To not publish the specifics of a product, but to point to always just subjective impressions instead, is an inacceptable methodology in technnology. So much so, that it cannot stand as an excuse for doing the right thing only incompletely.

If someone, as Danny, touches the border to respectibility we shall offer a helping hand for him to step over onto our side :D
 
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ctrl

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Distortion measurements taken outside of an anechoic chamber are irrelevant.
We can only hope that Danny knows better and is deliberately misleading people here.

Measurements in an anechoic chamber are of course optimal, but it is also possible with small quality compromises in a normal environment.

You just have to make sure that the first-order reflections are sufficiently damped. To do this, reduce the measurement distance to the DUT.
This means that you no longer capture all the influences of the baffle and the cabinet and the angle to the drivers becomes steeper (unless you measure each driver individually), but that is the compromise you have to make.

With this you can easily detect possible weak points of the speaker in terms of distortion.

For example, if the mic distance to the baffle is 30cm and the first reflecting surface is at a distance of 150cm (this is usually the floor and ceiling), then the first order reflections will travel a distance of roughly 300cm.

The sound pressure level drop for the first order reflections in the low bass range is thus at least -20dB (as usual the sound pressure decreases by 6dB with doubling the distance). In the worst case of optimal coherent summation or cancellation (reflections arrive delayed, i.e. out of phase), there is a ripple of +-1.5dB for the first two first order reflections of ceiling and floor. If the other reflecting surfaces (such as side walls) are at a greater distance, their contribution is small - more details how to do the calculation here. In reality, the ripple is likely to be rather less.

In addition, the first-order reflections at 30cm mic distance from the baffle are based on the speaker radiation of about 80° and thus their SPL is reduced even further as soon as the speaker no longer radiates omnidirectional.
1687949082550.png
Even with small baffles, there is more than -2dB SPL above 200Hz and more than -5dB attenuation of first order reflections above 600Hz.
Which leads to a ripple of less than +-1dB.

Harmonic distortion (HD) is the ratio of the harmonics to that of the fundamental component. This means that small errors due to the ripple caused by the first-order reflections are hardly significant.
With a ripple of +-1.5dB in the fundamental FR, the HD varies between 0.85% and 1.19% around the real value of 1% HD (1% means -40dB attenuation of HD signal).
So even the possible errors due to first order reflections in the low bass range hardly play a role and above 400-600Hz will be insignificant.

So, the real reason for his statement is probably more that his open baffle speakers will perform less well in such measurements and therefore will not be published.
 

JSmith

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Distortion measurements taken outside of an anechoic chamber are irrelevant.
It seems ol' Danny hasn't read any ASR speaker test review;
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.


JSmith
 

ctrl

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It seems ol' Danny hasn't read any ASR speaker test review;
The harmonic distortion measurements that Amir and Erin make are less accurate than they would be in anechoic chamber because of the room influences present.
Since the influences at a small measuring distance only slightly distort the result (see my post above), especially with increasing frequency, they are nevertheless meaningful.

Update: Got this wrong. See post#14 Erin seems to use room correction with HD measurements.
 
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fineMen

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The harmonic distortion measurements that Amir and Erin make are less accurate than they would be in anechoic chamber because of the room influences present.
Since the influences at a small measuring distance only slightly distort the result (see my post above), especially with increasing frequency, they are nevertheless meaningful.
I separated, distortion wise, a lot of bad drivers from a very few quite well drivers, when I was still into DIY. Now I'm convinced that my KEF R3 (old, outdated version) are the best ever in that regard. All was measured in my living room. How could I go so wrong?! ;)
It must be because I soon acknowledged the importance of intermodulation, phase distortion aka 'Doppler' included. Again not only measured, but exposed in the room I was going to use the speakers in. So wrong! ;)

Better never use a speaker actually, better just sell/buy, own it and talk a lot.
 

thewas

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For example, if the mic distance to the baffle is 30cm and the first reflecting surface is at a distance of 150cm (this is usually the floor and ceiling), then the first order reflections will travel a distance of roughly 300cm.
And as you know also a ground plane measurement can be performed, increasing those distances easily.

KEF-Reference-1-copy19.jpg

Source of photo: https://www.fidelity-online.de/kef-reference-1-messungen/
 

Curvature

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I separated, distortion wise, a lot of bad drivers from a very few quite well drivers, when I was still into DIY. Now I'm convinced that my KEF R3 (old, outdated version) are the best ever in that regard. All was measured in my living room. How could I go so wrong?! ;)
It must be because I soon acknowledged the importance of intermodulation, phase distortion aka 'Doppler' included. Again not only measured, but exposed in the room I was going to use the speakers in. So wrong! ;)

Better never use a speaker actually, better just sell/buy, own it and talk a lot.
You have no interest in the science of it?
 

ctrl

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At least he posts some measurements. Many speaker designers/makers don't post any.
Less likeable is the fact that Danny only attaches importance to measurements when it benefits him in business - not surprising, since he primarily wants to make money.

When selling cables of all kinds, there are no measurements, when competitor products are evaluated, then every detail of a measurement is judged very critically - also not surprising, since he wants to sell his speaker upgrade kits.

No superlative is omitted to describe the GR-Research top speaker series (quotes describing the NX-Series from the website):
End Game Open Baffle ...NX-Treme that will beat or compete with anything at any price point. ...NX-Otica is a pinnacle of open baffle loudspeaker designs.
In doing so, his own measurements (after all, they were posted online) show the design flaw of the NX series. Because these do not radiate like typical open baffle speakers, but show strong resonances that completely ruin the radiation pattern and no longer correspond to an open baffle (dipole) speaker.

Horizontal FR measurement (I assumed it's 0°-40°, but don't know for sure)
1687961928611.png
If we take these measurements and normalize them to the on-axis frequency response, the "design flaw" is easy to see:
1687962221360.png
Resonaces around 200Hz, 700Hz and 1100Hz. This is not the radiation pattern of what is claimed to be the "pinnacle of open baffle loudspeaker designs", but that of a speaker with strong resonances that ruin the OB radiation pattern. GR-Research should have noticed this already during the design of the speaker.

For comparison, here is the horizontal radiation pattern of a woofer (normalized to on-axis FR) in a normal OB speaker, such as those produced by spatialaudiolab.com (for example):
1687964143269.png1687964154347.png
More details about this can be found here.

Please don't get me wrong, the NX-Series speakers can still sound good as the human ear is relatively tolerant of errors, but these OB speakers are not the pinnacle of open baffle loudspeaker designs and other OB speakers can easily compete with these - at least technical design wise.

Thus, value is placed on measurements only under very, very specific conditions ;)
 
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abdo123

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The harmonic distortion measurements that Amir and Erin make are less accurate than they would be in anechoic chamber because of the room influences present.
Since the influences at a small measuring distance only slightly distort the result (see my post above), especially with increasing frequency, they are nevertheless meaningful.

Erin provides anechoic harmonic distortion measurements.

Amir used to as well (check the very early reviews) but then he noticed that it doesn't make much of a difference for his measurement enviroment so he stopped doing that.

Edit: a sample of when Amir used to do anechoic distortion measurements.

index.php
 

HarmonicTHD

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Erin provides anechoic harmonic distortion measurements.

Amir used to as well (check the very early reviews) but then he noticed that it doesn't make much of a difference for his measurement enviroment so he stopped doing that.

Edit: a sample of when Amir used to do anechoic distortion measurements.

index.php
Amir still provides THD and harmonics at 86 and 96dB SPL such as recently in this review for example.

Thread 'Focal SOLO6 ST6 Monitor Review'
https://audiosciencereview.com/forum/index.php?threads/focal-solo6-st6-monitor-review.45784/
 

ctrl

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Erin provides anechoic harmonic distortion measurements.

Edit: a sample of when Amir used to do anechoic distortion measurements.
Thanks for the clarification. Had only looked at Amir's last HD measurements - will modify my post above.

If the nearfield HD measurements are adjusted for room influences, then theoretically better results would be possible than using an anechoic chamber, since these always have a low cutoff frequency below which room influences are above +-1dB in the chamber.

With Erin's HD measurements, I miss the display of the FR to be able to assess the distortions in the low frequency range, since with quite a few speakers the frequency response already drops below 100Hz. Instead of 86dB, there are often only 80dB at 50Hz.
 

fineMen

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Thanks for the clarification. Had only looked at Amir's last HD measurements - will modify my post above.

If the nearfield HD measurements are adjusted for room influences, then ...
Nah, the HD is not of so much importance. My bass guitar, which has to be considered a relatively 'clean' musical instrument, generates 200% of harmonics aka 'distortion' easily. If there is another 10% (!) in effect may depend on my picking style more than on the speakers.

The HD of a speaker reveals systematic design errors or bad compromises. There are so many ... .

My personal finding is that literally no two way design must claim to be high fidelity. That is due to intermodulation and Doppler (in room) also. A quite subjective conclusion, but if it comes to GR research (research?!?) I still feel a little bit more informed.
 

ThatSoundsGood

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For me that doesn't sound like a good argument. To not publish the specifics of a product, but to point to always just subjective impressions instead, is an inacceptable methodology in technnology. So much so, that it cannot stand as an excuse for doing the right thing only incompletely.

If someone, as Danny, touches the border to respectibility we shall offer a helping hand for him to step over onto our side :D
On one hand I agree with you. I think it's important to be as transparent as possible and publish as much data as possible on why someone's speakers are great. On the other hand, Danny R has done a lot to get people into DIY and has sent them on a quest to learn. Sure, we might disagree with a lot of what he says and how he goes about it, but I still think there's a lot of value to it. I think it's cool that he helps people get into figuring their own way into all of this. Most people don't know how to read distortion data anyway. In fact, most people can't discern a good frequency response from a bad one. So there's a process to learning and he is a part of that for many people. I think people will outgrow him and find better products if they continue on the route, but maybe they get a set of NX-Oticas and that's where they land. It might be the best sounding speaker they've ever heard and it could bring them some great experiences. Sure, they have higher distortion or don't measure as well off-axis, but does that really matter if the experience is amazing? I've used some of his products and had good results. I've called the office and spoken with him. He was a total gentleman. Yes, he could have more detailed data. But he is providing a great service in many ways even if we disagree with some of his approach.
I don't see this as something where we are on opposing sides. Music is a uniter, not a divider.
 

fineMen

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I don't see this as something where we are on opposing sides. Music is a uniter, not a divider.
I get your drive with this, but I can't agree. As Einstein said ... ... don't over-simplificate. Speakers are tech/, music is something else. Let's keep them in their respective fields.

I only say: Burt Bacharach :cool:
 
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